The act of sticking up both middle fingers instead of just one, usually for added emphasis on the unspoken "fuck you" message.

In R is for Road Rage: "When one barrel just isn't enough, let loose with both arms to let them know you think they're especially big shit stabbers. An unintended side effect of the double deuce is that you will lose complete control of your car, so you'll swerve back and forth wildly for added effect."
-Maddox, The Alphabet of Manliness